Conventionally, a vehicle body floor structure has been known, which includes a dash cross member extending in a vehicle width direction on a vehicle inner side of a dash lower panel, wherein a lower end of the dash lower panel and a front end of a floor panel are joined together (for example, see Patent Document 1). In the vehicle body floor structure, position of a joint portion between the dash lower panel and the floor panel is set to be substantially the same as or behind a joint portion between the dash lower panel and the dash cross member. Further, in the vehicle body floor structure, an upper reinforcing member overlapping the floor panel is disposed in order to prevent deformation of the floor panel in the vicinity of feet of a driver due to a collision load. With such a vehicle body floor structure, the collision load input to a front side frame is transmitted rearward via the dash lower panel and the dash cross member.